Hex Lag Screw

Hex lag screws are large wood screws. Although the term “lag bolt” is often used to describe this product, technically they are a screw since lags are installed in wood by rotating the six-sided head. The lag thread is deeper and sharper than national coarse thread since it is designed to drive into wood and not to be used with a nut. Imported hex lag screws normally originate from Asia, possess a gimlet point, and meet the requirements of ASTM A307 Grade A. Portland Bolt can manufacture lag screws to meet other ASTM specifications or when the project requires domestically manufactured lag screws.

Manufacturing

Portland Bolt manufactures lag screws from 1/2″ diameter through 1-1/2″ diameter in most ASTM, AASHTO, and SAE specifications. Special tooling can be created to produce nonstandard head dimensions or bolt heads with your company’s name and/or logo.

Unless otherwise specified, nonstandard lag screws manufactured by Portland Bolt will possess a semi-cone point rather than a gimlet or cone point. A full point is unnecessary since a pilot hole nearly as large as the root diameter of the lag screw will need to be drilled prior to installation. Additionally, a gimlet point is designed for small diameter screws so they can be installed without a pilot hole. Lag screws in diameters listed in the above table do not require a gimlet point since too much torque would be required to install the large screws without drilling a pilot hole first. Without a pilot hole, the heads of the screws will often break before the lag is properly installed.

Stock

Standard Thread Length

The minimum thread length shall be equal to one-half the nominal screw length plus 1/2″ or 6”, whichever is less. One should consider longer than standard thread lengths for lag screws which are extremely long.

Note: Hex lag screws larger than 3/4″ in diameter and all square lag screws are rarely available in the marketplace as a stock item.

Hex Lag Dimensions

Click table to show drawing

Bolt
Diameter

D

F

H

Threads
Per
Inch

Thread Dimension

Body Diameter

Width Across
Flats

Head
Height

Pitch

TF

TD

TR

Max

Min

Flat
At
Root

Depth
of
Thread

Root
Diameter

1⁄2

0.515

0.482

3⁄4

11⁄32

6

0.167

0.072

0.064

0.371

5⁄8

0.642

0.605

15⁄16

27⁄64

5

0.200

0.086

0.077

0.471

3⁄4

0.768

0.729

11⁄8

1⁄2

41⁄2

0.222

0.096

0.085

0.579

7⁄8

0.895

0.852

15⁄16

37⁄64

4

0.250

0.108

0.096

0.683

1

1.022

0.976

11⁄2

43⁄64

31⁄2

0.286

0.123

0.110

0.780

11⁄8

1.149

1.098

111⁄16

3⁄4

31⁄4

0.308

0.133

0.119

0.887

11⁄4

1.277

1.223

17⁄8

27⁄32

31⁄4

0.308

0.133

0.119

1.012

13⁄8

1.404

1.346

21⁄16

29⁄32

3

0.333

0.143

0.128

1.119

11⁄2

1.531

1.469

21⁄4

1

3

0.333

0.143

0.128

1.244

Dimensions per ASME B18.2.1 2003

Stock Lag Screws

Length (in.)

Diameter

3/8"

1/2"

5/8"

3/4"

Plain

Galv.

Plain

Galv.

Plain

Galv.

Plain

Galv.

1

11375

11376

-

-

-

-

-

-

11⁄4

11377

11378

-

-

-

-

-

-

11⁄2

11379

11380

18904

18905

-

-

-

-

13⁄4

11381

11382

-

-

-

-

-

-

2

11383

11384

11413

11414

11447

11448

-

-

21⁄2

11385

11386

11415

11416

11449

11450

-

19575

3

11387

11388

11417

11418

11453

11454

11489

11490

31⁄2

11389

11390

11419

11420

11455

11456

11491

11492

4

11391

11392

11421

11422

11457

11458

11493

11494

41⁄2

11393

11394

11423

11424

11459

11460

-

-

5

11395

11396

11425

11426

11461

11462

11497

11498

51⁄2

11397

11398

18906

18907

18908

18909

-

-

6

11399

11400

11429

11430

11465

11466

11501

11502

7

11403

11404

11433

11434

11469

11470

11505

11506

8

11407

11408

11437

11438

11471

11472

11509

11510

9

-

-

11439

11440

11473

11474

11511

11512

10

11411

11412

11441

11442

11475

11476

11513

11514

11

-

-

-

-

18910

18911

18913

18914

12

18902

18903

11445

11446

11479

11480

11517

11518

14

-

-

18266

18267

11481

11482

11521

11522

16

-

-

18268

18269

19597

19545

11525

11526

18

-

-

18270

18271

19693

19694

11529

11530

20

-

-

-

-

-

-

18915

18916

These sizes are readily available in the marketplace and Portland Bolt stocks many of them in varying quantities. If you require a size that is not listed, Portland Bolt will manufacture them.